Got Homework?
Connect with other students for help. It's a free community.
Here's the question you clicked on:
 0 viewing
Help: CONTINUITY and removable discontinuity:
(attached below)
 8 months ago
 8 months ago
Help: CONTINUITY and removable discontinuity: (attached below)
 8 months ago
 8 months ago

This Question is Closed

PsymonBest ResponseYou've already chosen the best response.1
So you have 2 conditions to have a removable discontinuity. The first one is simply that the value must not be defined at that point, which is pretty obvious that is isn't because of the denominator. The second condition is basically the difference between whether or not you have an asymptote at your undefined point or simply a hole. The way to tell whether or not its an asymptote or a whole is if you factored your function, would the factor that is undefined cancel or remain? If the factor on bottom cancels, it is merely a hole, if it does not cancel then it is an asymptote and CANNOT be removed. So I would factor your numerator and see if the denominator cancels. If it does, then simply plug in 4 into your result and you'll get the value you're looking for.
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
can we work on this together?
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
i've tried doing this on my own but seem to be getting something wrong.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Sure. So I would factor the numerator and see if x4 cancels. If it cancels, you have a hole, if it does not cancel, you have an asymptote and it cannot be removed. You know how to factor the numerator, right?
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
i got 2(x^2+3x25) @Psymon
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
28you mean? And after that, you still have to further factor the x^2 + 3x  28.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Find factors of 28 that will add up to positive 3.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Right. So When you further factor the numerator, you should have 2(x±__)(x±__). Its just remember how to factor that x^2 + 3x  28 portion.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Exactly. In turn, that cancels out the denominator, which means the discontinuity is removable and not just an asymptote. Not only that, since the term that would make your function undefined disappeared, you can simply plug in 4 to find out the value you need.
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
we're left with 2 (x+7)
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
does this apply to every problem with continuity?
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Yes. Most of the work is finding a way to eliminate the portion that would give you an undefined answer. Once you manage that, you just plug in the value that the limit is approaching. Of course there are times when you cannot remove the undefined portion, in which that means the limit does not exist and you are merely approaching an asymptote.
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
ohhh can i practice a little, then ask you for a tricky problem like the one you just mentioned? it would really help.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
That works, I have no problem with that.
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
what about a JUMP DISCONTINUITY? same thing?
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
That's new terminology for me. I probably know what it is but have not heard it said that way. Could you give me an example?
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Ah, just one sided limits. We never really gave a name for it before, just that it had to do with onesided, lol.
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
oh so how do we begin with this one? sketch a graph?
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
i can do graphs but i'd like to do it a simpler way since i won't have enough time when it comes to a final
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
I apologize, I guess I was making sure what jump kind of meant since I did not have a picture. But yes, all you really need to confirm is that when x = 6 on both functions that they have different limits. It is pretty obvious that they do. As far as the left and right part goes, you need to see which function to just check and see which function is approaching from the left and which one is approaching from the right. Since 8x8 < 6, that must be the function approaching from the left. Therefore, f(6) of 8x8 is the value you will use for limit from the left. Since the other function is the one that will becoming from the right, it's value at x = 6 will be the value you use for the rightsided limit. Basically, you just need to see which function to plug the value into.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
The delay was graphing and looking at so I knew exactly what to say and to get my brain to work, lol.
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
it's okay, so how can we work this prob out?
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
dw:1375046904734:dw I know you know how to graph, but I wanted the visual up before we move on. So you just want to see which function is from the left and which one is from the right. When it gives you a piecewise function, it's pretty obvious which one is going to be coming from the left and which one from the right. Once you determine that, just plug in x = 6 into the graph that comes from the left and use that value for lim >6  Once you do that, plug x = 6 into the other function, since you know it's the one on the right, and find lim x> 6 +
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
A lot of the time you may have to determine the behavior on your own, but the piecewise just gave you the behavior so you didn't have to worry about it. From there it was just picking the correct function for left and for right.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
In regards to removable or nonremovable,it works the same way. if one of the functions has an asymptote at the jump point, then one of the sides or both may have a limit that DNE on that side, left or right. Maybe another example?
 8 months ago

mathcalculusBest ResponseYou've already chosen the best response.0
so to this problem we HAVE to sketch only?
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
In this case, no, because the piecewise function tells us which function to use on the left and on the right. The sketching would only come in if you had maybe one function that wasn't a piecewise. Like if the function was 1/[(2x^2 3] For something like that you would have to test points on the left and right and see if they're going up to infinity, down to negative infinity, etc. Any of these piecewise functions won't require s ketch, I just wanted to draw visual aid.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Holy cow my typing and grammar are horrible today o.o
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
Maybe if you have another jump problem we can look at it.
 8 months ago

PsymonBest ResponseYou've already chosen the best response.1
I'm going to need to head out, I apologize. Good luck with the limits.
 8 months ago
See more questions >>>
Your question is ready. Sign up for free to start getting answers.
spraguer
(Moderator)
5
→ View Detailed Profile
is replying to Can someone tell me what button the professor is hitting...
23
 Teamwork 19 Teammate
 Problem Solving 19 Hero
 Engagement 19 Mad Hatter
 You have blocked this person.
 ✔ You're a fan Checking fan status...
Thanks for being so helpful in mathematics. If you are getting quality help, make sure you spread the word about OpenStudy.